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Optimization of scleroglucan production by Sclerotium rolfsii by lowering pH during fermentation via oxalate
Tianlong Bai1,2, Teng Wang3, Yan Li2
1Applied Biology Laboratory, Shenyang University of Chemical Technology, Shenyang, 110142, China.
Background:
Sclerotium rolfsii is a potent producer of many secondary metabolites, one of which like scleroglucan is an exopolysaccharide (EPS) appreciated as a multipurpose compound applicable in many industrial fields.
Results:
Aspartate transaminase (AAT1) catalyzes the interconversion of aspartate and α-ketoglutarate to glutamate and oxaloacetate. We selected AAT1 in the oxalate metabolic pathway as a target of CRISPR/Cas9. Disruption of AAT1 leads to the accumulation of oxalate, rather than its conversion to α-ketoglutarate (AKG). Therefore, AAT1-mutant serves to lower the pH (pH 3-4) so as to increase the production of the pH-sensitive metabolite scleroglucan to 21.03 g L-1 with a productivity of up to 0.25 g L-1·h-1.
Conclusions:
We established a platform for gene editing that could rapidly generate and select mutants to provide a new beneficial strain of S. rolfsii as a scleroglucan hyper-producer, which is expected to reduce the cost of controlling the optimum pH condition in the fermentation industry.
